2,5-Dipicryl thiazoles

ABSTRACT

Heat resistant explosives of the formula   WHEREIN R is H or NO2 are prepared by contacting a picryl halide with a thiazole of the formula   WHEREIN X is halogen. The compound wherein R is NO2 may also be prepared by nitrating 2,5-dipicryl-1,3-thiazole.

United States atent n91 Sitzmann et al.

[ Nov. 25, 1975 2,5-DIPICRYL THIAZOLES [75] Inventors: Michael E. Sitzmann, Chevy Chase, Md.; Joseph C. Dacons, Washington, DC.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

221 Filed: on. 4, 1972 211 Appl. No.: 298,090

521 U.s.c|; ..260/302 R; 149/105 [51] Int. Cl. C07D 275/02 [58] Field of Search 149/105; 260/302 R [56] References Cited UNITED STATES PATENTS 3,505,320 4/1970 Dabritz et al. 260/302 R Primary ExaminerLeland A. Sebastian Attorney, Agent, or Firm-R. S. Sciascia; J. A. Cooke wherein R is 1-1 or N0 are prepared by contacting a picryl halide with a thiazole of the formula wherein X is halogen. The compound wherein R is N0 may also be prepared by nitrating 2,5-dipicryl- 1 ,3-thiazole.

3 Claims, No Drawings 2,5-DIPICRY L THIAZOLES BACKGROUND OF THE INVENTION This invention generally relates to explosives and more particularly to explosives with excellent heat sta-' bility.

Use of explosives in many different types of devices is widely known in the prior art. However, despite the huge number of explosives that are known there are relatively few that can withstand high temperatures in the range of 230260C or above without substantial deterioration. Since explosives in many specialized uses are subjected to temperatures of about 230C or higher there has been a constant search for explosive materials which will not deteriorate substantially due to high temperatures.

SUMMARY OF THE INVENTION Accordingly, one object of this invention is to provide new chemical compounds.

Another object of this invention is to provide chemical compounds that can be used as explosives.

A further object of this invention is to provide explosive compounds which are capable of withstanding temperatures in the range of 230-260C and above without substantial deterioration.

A still further object of this invention is to provide explosive compounds which can be used in environments wherein high temperatures are a problem (i.e., where aerodynamic heating is a problem).

Yet another object of this invention is to provide explosive compounds which can be used in mild detonating cord and flexible linear shaped charges.

These and other objects of this invention are accomplished by providing chemical compounds of the formula wherein R is H or N These-compounds are prepared by contacting a picryl halide with a thiazole of the formula wherein X is halogen under the standard conditions of the Ullmann biaryl synthesis. In the alternative, the

compound wherein R is N0 may also be prepared by nitrating 2,5-dipicryl-1,3-thiazole.

DESCRIPTION OF THE PREFERRED EMBODIMENT wherein R is H or NO can be prepared by contacting a picryl halide with 2,5-dihalo-1,3-thiazole under the standard Ullmann biaryl synthesis reaction conditions.

With the Ullmann synthesis the thiazole is dissolved in a solvent such as nitrobenzene and copper is added. The picryl halide, preferably picryl bromide, is then added dropwise as a solution in nitrobenzene, over a period of about 30 minutes while the temperature is maintained at about 145150C. Following this the solutions are purified using typical purification techniques.

Compounds wherein R is NO can also be prepared by a simple nitration of the 2,5-dipicryl-l,3-thiazole prepared by the Ullmann biaryl synthesis using the standard nitration procedures.

The general nature of the invention having been set forth, the following examples are presented as specific illustrations thereof. It will be understood that the invention is not limited to these specific examples but is susceptible to various modifications that will be recognized by one of ordinary skill in the art.

EXAMPLE I PICRYL BROMIDE An amount of 355 g (3.5 moles) of reagent grade potassium nitrate was dissolved in 800 ml of 30% oleum in a 2000 ml 3-neck round bottom flask fitted with a mechanical stirrer and a thermometer. During the addition of the potassium nitrate, the mixture was cooled and stirred on an ice bath, the temperature being .kept below 60C. When the addition was complete, the mixture was cooled to 30C and 79 g (0.5 moles) of bromobenzene was added at such a rate as to keep the temperature below 50C. The ice bath was then replaced by an oil bath and'the reaction mixture was heated to approximately 125C for four hours. After cooling, the mixture was drowned in crushed ice, the product was collected by filtration using a sintered glass funnel and thoroughly washed with water. After drying in a warm oven, it was dissolved in ml of acetone, 300 ml of methanol was added and the solution was cooled in the freeze compartment of the refrigerator. On filtration, 83.7 g of pale yellow crystalline picryl bromide, mp 122C (lit. 122-3C) was recovered. The filtrate was concentrated to about 150 ml by boiling on the steam bath and again cooled in the freeze compartment. The second crop weighed 28.0 g and melted over the range 11ll18C. On recrystallization from acetone-ethanol, an additional 21.0 g of crystalline product, mp 120-l22C was obtained to give a total yield melting at this temperature of 104.7 g, 71.6%. Samples melting at l22123C were obtained by one additional recrystallization from acetone-methanol.

EXAMPLE 2 2,5-DIPICRYL-1,3-THIAZOLE A stirred mixture of 58.4 g (0.24 mole) of 2,5- dibromothiazole and 137.4 g (2.16 mole) of copper in 210 ml of dry nitrobenzene was heated to C in a 1000 ml 3-neck round bottom flask equipped with a mechanical stirrer, thermometer and an addition funnel. A solution of 175.2 g (0.6 mole) of picryl bromide in 270 ml of dry nitrobenzene was added over a 20 minute period with the temperature of the reaction mixture maintained at 145l50C. The mixture was stirred at 145C for about 3 minutes after the addition was complete. The warm (ca 60C) reaction mixture was filtered and the insoluble material was washed with warm acetone until the washings were nearly colorless. Steam distillation removed the solvents from the filtrate leaving a dark solid residue. The water was removed by filtration and the dark solid product was washed with hot methanol. The methanol-insoluble material was dissolved in about 3 liters of hot acetone (with charcoal), the solution was filtered and the filtrate concentrated by distillation until precipitation occurred. Methanol was slowly added with continued distillation until the distillate temperature reached 60C. The warm mixture was filtered to give 79.0 g of product, mp 324-26 (dec.). Recrystallization of the product using the above acetone-methanol procedure gave 72.1 g (59.2% of the theoretical yield based on starting 2,5-dibromothiazole) of yellow crystals, mp 32930C (dec.).

EXAMPLE 3 2,5-DlPlCRYL-4-NlTRO-l ,3-THIAZOLE Potassium nitrate (42g, 0.375 mole) was added in portions to 100 ml of 30% oleum cooled below 60C. Thirty eight grams (0.075 mole) of 2,5-dipicrylthiazole was added rapidly in portions to the stirred potassium nitrate oleum mixture at 45C. The mixture was heated to 120C; all the solid material dissolved but after about 30 minutes precipitation from solution occurred. The mixture was stirred at l20l25C for 6.5 hours, then cooled to 40C and poured onto ice. The product (37.2 g, m.p. 26366C) was removed by filtration and washed with water and then with methanol.

The solid was dissolved in 400 ml of hot acetone, the solution was filtered, and the filtrate was concentrated by distllation to a volume of about 200 ml. Methanol (200 ml) was added and distillation was continued with the slow addition of more methanol until the distillate temperature reached 60C and the final volume was about 400 ml. The warm mixture was filtered to give 30.3 g (73.2%) of yellow solid, m.p. 26970C.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A thiazole of the formula 3. The thiazole of claim 1 wherein R is N0 

1. A THIAZOLE OF THE FORMULA
 2. The thiazole of claim 1 wherein R is H.
 3. The thiazole of claim 1 wherein R is NO2. 